A collaborative investigation of the molecular basis of cellular regulatory mechanisms is proposed. Included in the program are molecular geneticists, cellular physiologists, physical biochemists, and X-ray crystallographers working together in contiguous laboratories with shared facilities. Controls of cell growth rate in bacteria and aspects of the life cycle of yeast and phages will be studied. Protein-DNA interactions will be studied with the aim of elucidating the differential transcription underlying these physiological phenomena. Understanding of the roles played by membranes in regulatory processes will be furthered by genetic and physical studies on membrane structure and activities. Conformational changes in proteins resulting from ligand binding will be studied in several proteins by a variety of methods. Further details of protein structure will emerge from studies aimed at understanding factors influencing protein stability. Studies with phages will elucidate relationships between DNA replication and recombination and will determine the effects of nucleotide sequence on mutation rates. Long range projects to elucidate the molecular biology of perception are underway with bacteria and fish.